A transmission structure and control method for pressure control of a three-roll mill

Abstract

This invention discloses a transmission structure and control method for pressure control of a three-roll mill. The middle roller is mounted on the machine body at both ends. The front roller is rotatably mounted on a front roller adjusting frame via a central shaft, and the front roller adjusting frame is rotatably mounted on the machine body via a pivot point. The rear roller is rotatably mounted on a rear roller adjusting frame via a central shaft, and the rear roller adjusting frame is rotatably mounted on the machine body via a pivot point. Servo motors are respectively installed at the lower ends of the front and rear roller adjusting frames, and each servo motor is connected to a cam. A pressure acquisition mechanism is used to allow the cams to contact and collect the pressure on the contact surface. The servo motors drive the cams to rotate, causing the front or rear roller to move closer to or further away from the middle roller. This invention utilizes servo motors to drive the cams to rotate, which, in conjunction with the pressure acquisition mechanism, compresses the cams, thereby correspondingly driving the movement of the front or rear roller to control the gap between the front or rear roller and the middle roller, improving grinding efficiency and resulting in more stable output.

Description

Technical Field

[0001] This invention relates to the field of grinding structure and control technology, specifically to a transmission structure and control method for pressure control of a three-roll mill. Background Technology

[0002] Three-roll mills are widely used for wet grinding of raw materials in the chemical industry, including paints, inks, coatings, dyes, plastics, rubber, lead cores, leather, pharmaceuticals, food, cosmetics, and insulating materials. They offer multiple functions such as crushing, dispersing, emulsifying, homogenizing, and color matching. They enable highly uniform mixing of raw materials and can also recycle waste materials. Three-roll mills are suitable for grinding and dispersing products with high viscosity and fine particle size requirements. They offer good grinding performance, stable quality, easy operation, and easy color changing. A three-roll mill has three rollers mounted on an iron frame, centered on a straight line. It can be installed horizontally or slightly inclined. The grinding effect is achieved through the mutual pressing and friction at different speeds of the three horizontal rollers. The steel rollers can be hollow and water-cooled. Material is added between the middle and rear rollers. The three rollers can rotate in different directions, with the rotation speed increasing sequentially from back to front, thus producing excellent grinding action.

[0003] In daily grinding machine operation, precise control of the pressure between the rollers is crucial. Uneven pressure on both sides of the rollers leads to uneven grinding of the pigment, resulting in uneven thickness on one side and significantly impacting grinding quality and efficiency. Statistics show that many manufacturers in the domestic grinding machine industry have poorly designed transmission structures, making it difficult to control the pressure between each roller in a three-roll mill. This results in poor-quality material produced with each grinding cycle, necessitating repeated grinding and wasting considerable time, manpower, and resources.

[0004] Currently, there is a significant lack of high-efficiency grinding machines on the market. Many grinding machines adjust the gap between the front, middle, and rear rollers manually, a method that is inefficient and lacks precise pressure control, thus hindering accurate and efficient material grinding. While there are many three-roll grinding machines on the market that use pressure control, most of them independently control the pressure motors. This means that the pressure on both sides of the front and rear rollers is controlled by separate motors on either side. Independent motor control cannot guarantee synchronization between the two motors; when one motor is disturbed, the other cannot respond quickly enough. Furthermore, single-motor control is not well-suited to resisting load disturbances.

[0005] Therefore, there is an urgent need for a transmission structure and control method for pressure control of a three-roll mill to solve the problem of poor grinding efficiency. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a transmission structure and control method for pressure control of a three-roll mill, thereby solving the problem of poor grinding efficiency.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A transmission structure for pressure control of a three-roll mill, characterized in that it includes a machine body, a front roller adjusting frame, a rear roller adjusting frame, a front roller, a middle roller, a rear roller, a cam drive mechanism, and a pressure acquisition mechanism. The cam drive mechanism includes a cam and a servo motor. The two ends of the middle roller are mounted on the machine body. The front roller is rotatably mounted on the front roller adjusting frame via a front roller central shaft. The front roller adjusting frame is rotatably mounted on the machine body in front of the middle roller via a rotation fulcrum, and the front roller central shaft is offset from the rotation fulcrum on the front roller adjusting frame. The rear roller is mounted via a rear roller central shaft... The shaft is rotatably mounted on the rear roller adjusting frame, which is rotatably mounted on the machine body behind the middle roller via a rotating fulcrum, and the central shaft of the rear roller is offset from the rotating fulcrum on the rear roller adjusting frame; the lower ends of the front roller adjusting frame and the rear roller adjusting frame are respectively equipped with servo motors, and the output ends of the servo motors are respectively connected to the middle of a cam. The pressure acquisition mechanism is fitted to the side of the cam, which is used to allow the cam to abut and collect the pressure of the contact surface. The servo motor is used to drive the cam to rotate and drive the front roller or the rear roller to move closer to or away from the middle roller.

[0009] To optimize the above technical solution, the specific measures also include:

[0010] Furthermore, both the front roller adjusting frame and the rear roller adjusting frame include rotating connecting arms. The two ends of the front roller are rotatably mounted on the rotating connecting arms via the front roller central shaft. The rotating connecting arms at both ends of the front roller are rotatably mounted on the machine body on the front side of the middle roller via a rotating fulcrum. The rotating fulcrum on the front roller adjusting frame is located above the front roller central shaft, which is offset from the front roller central shaft. The two ends of the rear roller are rotatably mounted on the rotating connecting arms via the rear roller central shaft. The rotating connecting arms at both ends of the rear roller are rotatably mounted on the machine body on the rear side of the middle roller via a rotating fulcrum. The rotating fulcrum on the rear roller adjusting frame is located above the rear roller central shaft, which is offset from the rear roller central shaft.

[0011] Furthermore, the pressure acquisition mechanism includes a pressure sensing mechanism and a bolt B. The pressure sensing mechanism is mounted on the machine body via bolt B, and the acquisition end of the pressure sensing mechanism is always in contact with the side of the cam.

[0012] Furthermore, the pressure sensing mechanism includes a metal block, a contact arc surface, a stress strain gauge, and a stress strain acquisition circuit. The upper end of the metal block is provided with a contact arc surface that always fits against the side of the cam. On the metal block, below the contact arc surface, on both sides near and away from the cam, there is a groove symmetrically provided. The groove is provided with a stress strain gauge for sensing deformation. The stress strain acquisition circuit is connected to the stress strain gauge for acquiring and transmitting signals.

[0013] Furthermore, the pressure acquisition mechanism also includes bolt A, and the pressure sensing mechanism is mounted on the body via bolt B and bolt A which is misaligned with bolt B.

[0014] Furthermore, each of the front roller adjusting frames is provided with a cam drive mechanism at the lower end of both sides of the front roller, and each of the rear roller adjusting frames is provided with a cam drive mechanism at the lower end of both sides of the rear roller. Each of the cam drive mechanisms is respectively provided with a pressure acquisition mechanism.

[0015] Furthermore, the cam is a rotationally linearized cam designed according to an involute curve.

[0016] Furthermore, it also includes a rotating mechanism, which is connected to and drives the front roller and the rear roller to rotate respectively.

[0017] Furthermore, a control method is characterized by further including a constant pressure decoupling control system and a material output detection system. The constant pressure decoupling control system sends instructions to the servo motor of the corresponding cam drive mechanism via a CAN bus, and controls the rotation of the cam on the servo motor. The cam drives the left or right side of the front roller adjustment frame, or the left or right side of the rear roller adjustment frame, which serves as the transmission mechanism, to move, thereby adjusting the distance between the two sides of the front or rear roller and the middle roller. The material output detection system is used to detect whether the material output is qualified. If the detection is qualified, the material is directly discharged. If the detection is unqualified, the detection result is fed back to the constant pressure decoupling control system to adjust the speed of the servo motors on both sides of the front or rear roller, thereby controlling the distance between the two sides of the front or rear roller and the middle roller until the discharge is qualified.

[0018] Furthermore, the constant pressure decoupling control system includes a touch screen system for monitoring and controlling the servo motor, a pressure ring slip mold controller, and a decoupling controller. The lower ends of both sides of the front roller adjusting frame and the rear roller adjusting frame are respectively provided with a cam drive mechanism and a pressure acquisition mechanism. The touch screen system sends instructions to the servo motor of the corresponding cam drive mechanism through the CAN bus, and controls the rotation of the cam on it through the servo motor.

[0019] The actual positions of the two servo motors on both sides of the front roller adjustment frame are collected using a touch screen system. The actual position of each servo motor is subtracted from the input position to obtain the tracking error. The actual position of one servo motor is multiplied by a disturbance coefficient to obtain the load disturbance of the other servo motor. This disturbance is added to the actual position of the original servo motor and then multiplied by the stress-strain pressure coefficient to obtain the actual pressure value. The difference between the actual pressure values ​​of the two servo motors is used to obtain the synchronization error.

[0020] The system consists of two servo motors, servo motor A and servo motor B. For servo motor A, the input is a pressure setpoint. The pressure is converted into a position value and input to servo motor A using a calibrated stress-strain coefficient. The actual position of servo motor B is multiplied by a disturbance coefficient to obtain the load disturbance of servo motor A. The actual position of servo motor A plus the load disturbance is fed back to the input, and the difference between the input and the actual position is used to obtain the position tracking error of servo motor A. The actual position of servo motor A and the load disturbance are added together and multiplied by the stress-strain gain to obtain the actual pressure value of servo motor A. The difference between this actual pressure value and the actual pressure value of servo motor B is used as the input to the decoupling controller. The decoupling controller feeds back the pressure difference between the two sides to the pressure ring slip mode controller through the decoupling coefficient to adjust the position of the two servo motors. This allows the pressure on both sides of the front roller to stabilize after a short period of fluctuation. The rear roller uses the same control.

[0021] The beneficial effects of this invention are:

[0022] This invention utilizes a servo motor to drive a cam rotation, which, in conjunction with a pressure acquisition mechanism, compresses the cam, thereby correspondingly moving the front or rear roller. The cam's rotation performs linear motion, capable of completing various complex movements, including linear motion, oscillation, constant-speed motion, and non-constant-speed motion. Therefore, the servo motor can effectively control the pressure between the front or rear roller and the middle roller via the cam. For example, when the cam rotates and compresses the pressure acquisition mechanism, the front roller adjustment frame, which controls the movement of the front roller, is driven by the cam to oscillate around its pivot point, thus moving the front roller and changing the gap between the front and middle rollers. The structure in this design uses a servo motor to drive the cam in linear motion, thereby precisely controlling the pressure between the front and middle rollers. This reduces the error of manual pressure control, allowing the grinder to adjust different pressures for different grinding materials, improving grinding efficiency. By controlling the pressure between each roller as needed for different materials, the three-roll grinder achieves higher raw material utilization and more stable output.

[0023] The structure of this invention controls the pressure on both sides of the front and middle rollers, as well as the rear and middle rollers, which can be changed according to the needs of the grinding material. It has the advantages of conveniently adjusting the pressure between the front, middle, and rear rollers. It solves the problem of the practicality of three-roll mills, which cannot be practically improved because the pressure between the front, middle, and rear rollers cannot be properly adjusted, resulting in the inability to change the size and thickness of the ground material and the inability to adjust the pressure according to different grinding materials.

[0024] This invention controls the rotation of a cam by positioning a servo motor through a control system. This cam then compresses the cam against a surrounding pressure sensing mechanism. A rotating linkage arm and other structures alter the pressure between one side of the front roller and the middle roller. The ground material is collected and tested. Feedback is provided to the control system based on the test results. Qualified material is discharged directly, while unqualified material is addressed by the control system, which sends instructions to the corresponding servo motor to adjust its rotation and thus the pressure between the front and middle rollers. The pressure difference between the two ends of the rollers is calculated and input to the two servo motors via a decoupling control algorithm, becoming part of their control commands. Dynamic compensation using a sliding mode controller maintains the pressure between the rollers near a set value, improving control stability and meeting high precision requirements, thereby enhancing grinding quality and efficiency. Attached Figure Description

[0025] Figure 1 This is a structural side view of a transmission structure for pressure control of a three-roll mill proposed in this invention;

[0026] Figure 2 This is a schematic diagram of a cam structure for a transmission structure used in pressure control of a three-roll mill, as proposed in this invention.

[0027] Figure 3 This is a schematic diagram of the pressure sensing mechanism of a transmission structure for pressure control of a three-roll mill proposed in this invention.

[0028] Figure 4 This is a flowchart of a control method for a transmission structure used for pressure control of a three-roll mill, as proposed in this invention.

[0029] Figure 5 This is a diagram showing the rotation angle relationship of a servo motor in a transmission structure for pressure control of a three-roll mill, as proposed in this invention.

[0030] Figure 6 This is a diagram showing the relationship between the front roller movement distance of a transmission structure for pressure control of a three-roll mill proposed in this invention.

[0031] Figure 7This is a structural block diagram of a decoupled control system for a transmission structure used in pressure control of a three-roll mill, as proposed in this invention.

[0032] Reference numerals: 1-Rotating linkage arm, 2-Pressure sensing mechanism, 3-Bolt B, 4-Bolt A, 5-Cam, 6-Servo motor, 7-Front roller central shaft, 8-Front roller, 9-Rotating fulcrum, 10-Middle roller, 11-Rear roller, 12-Rear roller central shaft, 13-Machine body, 14-Stress strain gauge, 15-Contact arc surface, 16-Stress strain acquisition circuit. Detailed Implementation

[0033] The invention will now be described in further detail with reference to the accompanying drawings.

[0034] As attached Figure 1 As shown, an embodiment of the present invention provides a transmission structure for pressure control of a three-roll mill, comprising a machine body 13, a front roller adjusting frame, a rear roller adjusting frame, a front roller 8, a middle roller 10, a rear roller 11, a cam drive mechanism, and a pressure acquisition mechanism. The cam drive mechanism includes a cam 5 and a servo motor 6. The two ends of the middle roller 10 are mounted on the machine body 13. The front roller 8 is rotatably mounted on the front roller adjusting frame via a front roller central shaft 7. The front roller adjusting frame is rotatably mounted on the machine body 13 in front of the middle roller 10 via a rotation fulcrum 9, and the front roller central shaft 7 is misaligned with the rotation fulcrum 9 on the front roller adjusting frame. The rear roller 11 is rotated via a rear roller central shaft 12. The front roller adjustment frame is mounted on the rear roller adjustment frame, which is rotatably mounted on the machine body 13 behind the middle roller 10 via a rotation fulcrum 9. The central shaft 12 of the rear roller is offset from the rotation fulcrum 9 on the rear roller adjustment frame. The lower ends of the front roller adjustment frame and the rear roller adjustment frame are each equipped with a servo motor 6. The output end of the servo motor 6 is connected to the middle of a cam 5. The pressure acquisition mechanism is fitted to the side of the cam 5 to allow the cam 5 to abut and collect the pressure of the contact surface. The servo motor 6 is used to drive the cam 5 to rotate and drive the front roller 8 or the rear roller 11 to move closer to or away from the middle roller 10 around their respective rotation fulcrum 9.

[0035] In use, this invention utilizes a servo motor 6 to drive the cam 5 to rotate, which, in conjunction with a pressure acquisition mechanism, compresses the cam 5, thereby correspondingly moving the front roller 8 or the rear roller 11. The cam 5 rotates in a linear motion, capable of performing various complex movements, including linear motion, oscillation, constant-speed motion, and non-constant-speed motion. Therefore, the servo motor 6 can effectively control the pressure between the front roller 8 or rear roller 11 and the middle roller 10 via the cam 5. For example, when the cam 5 rotates and compresses the pressure acquisition mechanism, the front roller adjustment frame, which controls the movement of the front roller 8, is driven by the cam 5 to oscillate around its rotational fulcrum 9, thus moving the front roller 8 and changing the pressure between the front roller 8 and the middle roller 10. The structure in this design uses the servo motor 6 to drive the cam 5 in a linear motion, thereby precisely controlling the pressure between the front roller 8 and the middle roller 10. This reduces the error of manual pressure control, allowing the grinder to adjust different pressures for different grinding materials, improving grinding efficiency, and enabling the three-roll grinder to control different pressures between rollers as needed for different materials. This results in higher raw material utilization and more stable output for the three-roll grinder.

[0036] The structure of this invention controls the pressure between the front roller 8 and the middle roller 10, as well as the pressure between the rear roller 11 and the middle roller 10, which can be changed according to the needs of the grinding material. It has the advantages of conveniently adjusting the pressure between the front roller 8, the middle roller 10 and the rear roller 11. It solves the problem that the size and thickness of the ground material cannot be changed due to the inability to properly adjust the pressure between the front roller 8, the middle roller 10 and the rear roller 11, which greatly reduces the practicality of the three-roll mill.

[0037] Specifically, cam 5 presses against the pressure acquisition mechanism on one side. The servo motor 6 controls the rotation of cam 5 via the rotation of its motor shaft. The rotation of cam 5 is a linear motion. This linear motion of cam 5, combined with the pressure acquisition mechanism, causes cam 5 to move to the other side of the pressure, driving the corresponding front roller adjusting frame to swing around its pivot point 9. During this swing, the front roller 8 on the front roller adjusting frame moves accordingly. Since the position of the middle roller 10 is fixed, the distance between the front roller 8 and the middle roller 10 can be changed, thereby controlling the pressure. The pressure between the front roller 8 and the middle roller 10 can be controlled by adjusting the distance of the linear motion of cam 5 based on the rotation angle of the servo motor 6. In this design, the pressure acquisition mechanism is used for zero-position setting and is connected to the cam.

[0038] In another specific embodiment based on the above, both the front roller adjusting frame and the rear roller adjusting frame include a rotating linkage arm 1. The two ends of the front roller 8 are rotatably mounted on the rotating linkage arm 1 via the front roller central shaft 7. The rotating linkage arms 1 at both ends of the front roller 8 are rotatably mounted on the machine body 13 on the front side of the middle roller 10 via the rotating fulcrum 9, and the rotating fulcrum 9 on the front roller adjusting frame is located above the front roller central shaft 7, which is offset from the front roller central shaft 7. The two ends of the rear roller 11 are rotatably mounted on the rotating linkage arm 1 via the rear roller central shaft 12. The rotating linkage arms 1 at both ends of the rear roller 11 are rotatably mounted on the machine body 13 on the rear side of the middle roller 10 via the rotating fulcrum 9, and the rotating fulcrum 9 on the rear roller adjusting frame is located above the rear roller central shaft 12, which is offset from the rear roller central shaft 12.

[0039] In this embodiment, the servo motor 6 can be placed inside the body 13 with one side of the servo motor 6's rotation shaft facing outward. The cam 5 is fixed on the rotation shaft of the servo motor 6, and one side of the servo motor 6's rotation shaft is fixed to the rotating linkage arm 1 with three screws.

[0040] In another specific embodiment based on the above, the pressure acquisition mechanism includes a pressure sensing mechanism 2 and a bolt B3. The pressure sensing mechanism 2 is mounted on the body 13 by the bolt B3, and the acquisition end of the pressure sensing mechanism 2 is always in contact with the side of the cam 5. In this embodiment, the acquisition end of the pressure sensing mechanism 2 can be initially positioned to contact the side with the smallest rotational distance from the cam 5.

[0041] As attached Figure 3 As shown, in a further embodiment, the pressure sensing mechanism 2 includes a metal block, a contact arc surface 15, a stress strain gauge 14, and a stress strain acquisition circuit 16. The upper end of the metal block is provided with a contact arc surface 15 that always fits against the side of the cam 5. On the metal block, below the contact arc surface 15, on both sides near and away from the cam 5, a groove is symmetrically provided. The groove is provided with a stress strain gauge 14 for sensing deformation. The stress strain acquisition circuit 16 is connected to the stress strain gauge 14 for acquiring and transmitting signals.

[0042] In use, for example, the pressure on both sides of the front roller 8 is transmitted downwards to the cam 5 through the rotating connecting rod arm 1 fixed at the top. The cam 5, through the pressure sensing mechanism 2, transmits the pressure to the strain gauge 14. The strain gauge 14 deforms under pressure, generating stress and strain inside. This stress and strain is the direct response of the sensitive element to external pressure. The stress and strain acquisition circuit 16 uses the piezoresistive effect to convert this stress and strain into a corresponding electrical signal, which is then transmitted to the signal conditioning circuit. The signal conditioning circuit amplifies, filters, and linearizes the received electrical signal to improve its stability and accuracy. It typically includes modules such as amplifiers, filters, and ADC analog-to-digital converters. The device can amplify the weak signal output by the sensor to a range suitable for subsequent processing. The filter can remove noise and interference signals. The ADC102 analog-to-digital converter converts the processed analog signal into a digital signal, making the signal processable. Then, the processed digital signal is output to the controller through the output circuit. The controller performs corresponding processing based on the obtained digital signal. The output circuit is used to convert the signal-conditioned electrical signal into a readable or processable form. Depending on the specific application requirements, the output can be an analog signal such as voltage or current, or a digital signal such as a serial communication interface. The output circuit can also include a calibration circuit to calibrate the sensor output and improve the measurement accuracy.

[0043] Among them, the stress-strain gauge 14 is based on the interaction between the internal stress and the resulting deformation of an object when it is subjected to external forces. Stress is a physical quantity that describes the additional internal force per unit area inside an object, which can be caused by external forces such as tension, compression, shear, or bending. Strain, on the other hand, describes the change in shape or size of an object under the action of external forces. The relationship between stress and strain is usually described by Hooke's Law. Within the elastic range, that is, when the stress on the object does not exceed its elastic limit, the relationship between stress and strain is linear. The pressure at both ends of the front roller 8 and the middle roller 10 is transferred to the stress-strain gauge 14, and the pressure data can be obtained through stress-strain calculation.

[0044] In a further embodiment, the pressure acquisition mechanism also includes bolt A4. The pressure sensing mechanism 2 is mounted on the body 13 via bolt B3 and bolt A4, which is misaligned with bolt B3. After bolt B3 limits the pressure sensing mechanism 2, it can be finely adjusted as needed, and then fully tightened by the misaligned bolt A4.

[0045] In another specific embodiment based on the above, a cam drive mechanism is provided at the lower ends of both sides of the front roller adjustment frame and a cam drive mechanism is provided at the lower ends of both sides of the rear roller 11. Each cam drive mechanism is respectively provided with a pressure acquisition mechanism.

[0046] As attached Figure 2As shown, in another specific embodiment based on the above, cam 5 is a rotationally linearized cam designed according to an involute curve.

[0047] In another specific embodiment based on the above, a rotating mechanism is also included, which is connected to and drives the front roller 8 and the rear roller 11 to rotate respectively. In this solution, the middle roller 10 is provided with a central shaft 10 as needed, and the rotating mechanism can be connected to the central shaft 10 as needed and drive the middle roller 10 to rotate. In this solution, the rotation of the front roller 8 or the rear roller 11 can also be controlled by connecting the central shaft 7 of the front roller and the central shaft 12 of the rear roller respectively through an asynchronous motor, or driven by gears for grinding materials.

[0048] As attached Figure 4 As shown, a transmission structure and control method for pressure control of a three-roll mill also includes a constant pressure decoupling control system and a material output detection system. The constant pressure decoupling control system sends commands to the servo motor 6 of the corresponding cam drive mechanism via a CAN bus, and controls the rotation of the cam 5 on the servo motor 6. The cam 5 drives the left or right side of the front roller adjustment frame, or the left or right side of the rear roller adjustment frame, which serves as the transmission mechanism, to move, thereby adjusting the distance between the two sides of the front roller 8 or rear roller 11 and the middle roller 10. The material output detection system is used to detect whether the material output is qualified. If the detection is qualified, the material is directly discharged. If the detection is unqualified, the detection result is fed back to the constant pressure decoupling control system, which adjusts the speed of the servo motor 6 on both sides of the front roller 8 or rear roller 11, thereby controlling the distance between the two sides of the front roller 8 or rear roller 11 and the middle roller 10 until the discharge is qualified.

[0049] As attached Figure 7 As shown, the constant pressure decoupling control system further includes a touch screen system for monitoring and controlling the servo motor 6, a pressure ring slip mold controller and a decoupling controller. The lower ends of both sides of the front roller adjusting frame and the rear roller adjusting frame are respectively provided with a cam drive mechanism and a pressure acquisition mechanism. The touch screen system sends instructions to the servo motor 6 of the corresponding cam drive mechanism through the CAN bus, and controls the rotation of the cam 5 on it through the servo motor 6.

[0050] The actual positions of the two servo motors 6 on both sides of the front roller adjustment frame are collected using a touch screen system. The actual position of each servo motor 6 is subtracted from the input position to obtain the tracking error. The actual position of one servo motor 6 is multiplied by a disturbance coefficient to obtain the load disturbance of the other servo motor 6. This disturbance is added to the actual position of the original servo motor 6 and then multiplied by the stress-strain pressure coefficient to obtain the actual pressure value. The difference between the actual pressure values ​​of the two servo motors 6 is used to obtain the synchronization error.

[0051] The two servo motors 6 are divided into servo motor A and servo motor B. For servo motor A, the input is the pressure setpoint. The pressure is converted into a position value and input to servo motor A through the calibrated stress-strain coefficient. The actual position of servo motor B is multiplied by the disturbance coefficient as the load disturbance of servo motor A. The actual position of servo motor A plus the load disturbance is fed back to the input terminal, and the position tracking error of servo motor A is obtained by subtracting it from the input position. The actual position of servo motor A and the load disturbance are added together and multiplied by the stress-strain gain to obtain the actual pressure value of servo motor A. The difference between the actual pressure value of servo motor A and the actual pressure value of servo motor B is used as the input of the decoupling controller. The decoupling controller feeds back the pressure difference between the two sides to the pressure ring slip mode controller through the decoupling coefficient to adjust the position of the two servo motors 6, so that the pressure on both sides of the front roller 8 tends to stabilize after a short period of fluctuation. The rear roller 11 adopts the same control.

[0052] The pressure loop sliding mode control and decoupling control include sliding mode control of the pressure and decoupling control based on the difference between the actual pressure values ​​of the two servo motors 6. For sliding mode control of the pressure loop, the main steps are sliding surface design, control law design, and controller implementation. The main step for decoupling control of the pressure difference is tuning the decoupling coefficients for the pressure differences between the two servo motors.

[0053] During use, the pressure on both sides of the front roller 8 is set to a constant value according to the grinding requirements of the material. When grinding begins, the addition of material causes the pressure on both sides of the front roller 8 to change. Due to the pressure change, one side of the front roller 8 is displaced. Since the other side is coupled to the first side, the other side will also shift based on the coupling factor due to the displacement of the first side. This causes the pressure on both sides of the front roller 8 to change. At this time, the decoupling controller will feed back the pressure difference between the two sides to the pressure ring slip mold controller through the decoupling coefficient, thereby adjusting the position of the servo motors 6 on both sides. This makes the pressure on both sides of the front roller 8 stabilize after a short period of fluctuation, without affecting the grinding of the material and ensuring the grinding accuracy.

[0054] When using this invention:

[0055] Set to zero:

[0056] First, secure the lower end of the pressure sensing mechanism 2 with bolt A4. Hold the upper end of the pressure sensing mechanism 2 against your hand, and simultaneously control the servo motor 6 to rotate, causing the cam 5 to rotate. When the top of the cam 5 is in contact with the pressure sensing mechanism 2, secure the upper end of the pressure sensing mechanism 2 with bolt B3 to complete the zero-position setting. The encoder inside the servo motor 6 remembers the zero point position after the zero-position setting, facilitating subsequent zero-return operations.

[0057] Detailed operation process:

[0058] Compared to manually controlling the distance between the front roller 8 and the middle roller 10, this scheme controls the distance between the front roller 8 and the middle roller 10, as well as between the middle roller 10 and the rear roller 11, by controlling the rotation of the servo motor 6, making the pressure control more precise. For pressure control, pressure is input to the servo motor 6, and the position of the servo motor 6 is controlled by sliding mode control in the pressure loop. To address the mutual influence of the pressure of the two servo motors 6, decoupling control is used. The pressure loop input of the two servo motors 6 is increased by multiplying the pressure difference between the two servo motors 6 by the tunable decoupling coefficient, so that each servo motor 6 can decouple the pressure load disturbance of the other servo motor 6, thereby maintaining the stability of pressure control and improving the control accuracy.

[0059] For the pressure controller, a sliding mode controller is used in the design. The design of the sliding mode controller u is as follows:

[0060] u = u eq +u sw

[0061] In the formula: u eq It is equivalent control, capable of tracking the state of the controller system, that is, keeping the system state on the sliding surface at all times; u sw It is a switching control that brings the system state closer to the sliding surface, thereby reducing system chattering.

[0062] The sliding mode switching function s is designed as follows:

[0063] s = c1e1 + c2e2 + e3

[0064] In the formula: c1 and c2 are the desired poles, which determine the dynamic quality of the sliding mode.

[0065] The differential equation for sliding mode motion is:

[0066]

[0067] In the formula: e1, e2, and e3 are the system errors, ω h Let ξ be the natural frequency of the system. h Let K be the damping ratio of the system. h The gain of the system output relative to the input.

[0068] Using the exponential reaching law, in the equivalent control part, differentiating s = c1e1 + c2e2 + e3 yields:

[0069]

[0070] according to Equivalent control can be obtained:

[0071]

[0072] The switching control section is as follows:

[0073] u sw =-εsgn(s)-ks

[0074] In the formula: sgn(s) is the exponential rate of convergence.

[0075] In summary, the design of the sliding mode controller is as follows:

[0076]

[0077] In the formula: ε is the width of the sliding surface, and k is the parameter of the exponential reaching rate.

[0078] For example, the pressure input to the controller system is calibrated by the sliding mode controller and then enters the position controller. The position controller uses simple proportional control. After passing through the position controller, because the initial set positions of the two servo motors 6 are different, when the servo motors 6 perform position control, the two ends of the controlled front roller 8 will deviate due to the different initial positions of the servo motors 6. A change in the position of the servo motor 6 on one side of the front roller 8 will cause the roller on that side to shift, thereby causing the other side of the roller to shift as well. This makes the two sides of the roller mutually coupled, and the position control of the two servo motors 6 mutually coupled. Consequently, the pressure on both sides of the roller is also mutually coupled.

[0079] For the pressure coupling between the two servo motors 6, it is simplified to the position coupling between the two servo motors 6, hereinafter referred to as motor 1 and motor 4. The position difference between the position of motor 1 at the current moment and the position of motor 1 at the previous moment is multiplied by the coupling coefficient and added to the output position of motor 2, which is the coupling of motor 1 to motor 2. Similarly, the position difference between the position of motor 2 at the current moment and the position of motor 2 at the previous moment is multiplied by the coupling coefficient and added to the output position of motor 1, which is the coupling of motor 2 to motor 1.

[0080] To address the issue of pressure coupling on both sides of the roller due to the mutual coupling of motor positions, a decoupling controller is used to solve this problem. The difference between the output pressures of the coupled motor 1 and motor 2 is fed into the decoupling controller. After being multiplied by the decoupling coefficient of the decoupling controller, the output result is fed back to the pressure sliding mode controller as part of the input of the pressure sliding mode controller, thereby adjusting the position of the two motors and changing the pressure of the two motors, thus achieving decoupling control of the pressure.

[0081] In position control mode, the controller adjusts the output of the servo motor 6 to reach a predetermined position. The servo motor 6 controls the rotation of the motor shaft, thereby controlling the rotation of the cam 5. The cam 5 moves linearly and presses against the pressure sensing mechanism 2, which is fixed at the zero position on its left side, thus moving to the right. The movement of the cam to the right drives the pressure sensing mechanism 2, which is fixed on its outer side, to move, thereby changing the distance between the front roller 8 and the middle roller 10.

[0082] The servo motor 6 controls the rotation of its motor shaft, thereby controlling the rotation of the cam 5 connected to the motor shaft. The rotation of the cam 5 is pressed against the pressure sensing mechanism 2 on its left side, which is used for zero-position setting and pressing against the cam 5, thereby controlling the movement of the front roller 8.

[0083] The control system, which monitors and controls the servo motors via a touchscreen, controls the rotation of motors 1 and 2 through a CAN bus. The two motors, in turn, control the rotation of cams 5 on both sides through their respective motor shafts. Cams 5 control the movement of the left and right sides of the front roller, thereby controlling the gap between the two sides of the front roller 8. The front roller 8 outputs the material. The material is inspected to determine whether the material is qualified. Qualified material is discharged directly. For unqualified material, the uniformity is observed to determine which side of the front roller needs pressure adjustment. This feedback is then sent to the control system, which adjusts the speed of the servo motors on both sides based on the feedback data, thereby controlling the gap to ensure that the material output meets the requirements.

[0084] On a plane, as a moving straight line (generating line) rolls along a fixed circle (base circle), the trajectory of any point on this straight line is called an involute of this base circle. Based on the principle of the involute curve, the servo motor 6 controls the rotation angle of its motor shaft, which in turn controls the linear rotation angle of the cam 5, thereby controlling the distance the front roller 8 moves. The rotation angle of the servo motor 6's motor shaft is directly proportional to the distance the front roller 8 moves. (See attached diagram) Figure 5 As shown:

[0085]

[0086] In the formula: It is the roll angle, r is the radius of the circle, and X is the roll angle. k Let k be the x-coordinate, Y k Let k be the ordinate of point k.

[0087] As attached Figure 6 As shown, CD is the distance the front roller 8 moves, and AB is the distance mapped from a point on cam 5 to the two-dimensional coordinate system. Therefore, based on the similarity between triangle OCD and triangle OAB, the distance CD that the front roller 8 moves can be calculated.

[0088]

[0089] In the formula: d is the length of CD, l1 is the length of AO, and l2 is the length of CO.

[0090] That is, the distance that the front roller 8 moves is calculated as follows: This allows us to determine the relationship between the distance the front roller 8 moves and the angle at which the servo motor 6 rotates.

[0091] The method of this invention can improve control stability and synchronization performance: when one motor is disturbed, the other motor can respond quickly to maintain synchronization between the two; enhance system robustness: the dual-motor system can better resist load disturbances, improve system stability and robustness, and this decoupled control method enables rapid adjustment to maintain system balance and keep pressure output stable when one motor is disturbed by the other motor; improve control accuracy: achieve multi-objective control, reduce current and torque ripple, and improve the dynamic and steady-state performance of the system.

[0092] This invention uses a control system to position the servo motor 6 to control the rotation of the cam 5, which then compresses the cam with the surrounding pressure sensing mechanism 2. The pressure between one side of the front roller 8 and the middle roller 10 is changed through structures such as rotating linkage arms. The ground material is collected and tested. Based on the test results, the control system receives corresponding feedback. Qualified material is discharged directly, while unqualified material is given instructions to the corresponding servo motor 6 based on the control system's judgment. The servo motor 6's rotation is adjusted to regulate the pressure between the front roller and the middle roller. The pressure sensing mechanism 2, designed based on stress and strain, detects and monitors the pressure between the rollers. Based on the detected pressure, a pressure control system is designed, including the acquisition and calculation of the two servo motor states, feedforward compensation, and decoupling control. The pressure difference between the two ends of the rollers is calculated and input to the two servo motors 6 through the decoupling coefficient of the decoupling control algorithm, becoming part of the control instructions for the two servo motors 6. Dynamic compensation is achieved through a sliding mode controller. This is a very ingenious transmission structure and control method for pressure control. This solution uses a constant pressure decoupling control method to maintain the pressure between the rollers near the set value, improving control stability and meeting the high precision requirements of control. It also solves the problem of the output pressure of motor 2 affecting the disturbance of motor 1, enabling the three-roll mill to maintain the pressure at both ends near the input value in pressure mode, thus improving stability and improving grinding quality and efficiency.

[0093] This invention improves grinding efficiency: by precisely controlling the pressure between the rollers, materials can be ground more effectively. Appropriate pressure allows for sufficient compression and friction between the rollers, thus improving grinding efficiency and quality. It also protects the rollers and equipment: pressure control helps avoid excessive pressure between the rollers, preventing damage or excessive wear and extending equipment lifespan. Furthermore, it adapts to different materials: different materials require different grinding pressures. The pressure control mode allows for easy adjustment of the pressure between the rollers to meet the grinding needs of different materials. Finally, it enables automated operation: the pressure control mode can be combined with an automatic control system to automate the grinding process. This not only reduces the burden on operators but also improves production efficiency and minimizes the impact of human factors on product quality.

[0094] It should be noted that the terms such as "upper", "lower", "left", "right", "front", and "back" used in the invention are only for clarity of description and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0095] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A control method for a transmission structure used in pressure control of a three-roll mill, characterized in that: The transmission mechanism includes a machine body, a front roller adjusting frame, a rear roller adjusting frame, a front roller, a middle roller, a rear roller, a cam drive mechanism, and a pressure acquisition mechanism. The cam drive mechanism includes a cam and a servo motor. The two ends of the middle roller are mounted on the machine body. The front roller is rotatably mounted on the front roller adjusting frame via a front roller central shaft. The front roller adjusting frame is rotatably mounted on the machine body in front of the middle roller via a rotation fulcrum, and the front roller central shaft is offset from the rotation fulcrum on the front roller adjusting frame. The rear roller is rotatably mounted on the rear roller adjusting frame via a rear roller central shaft. The rear roller adjusting frame is rotatably mounted on the machine body behind the middle roller via a rotation fulcrum, and the rear roller central shaft is offset from the rotation fulcrum on the rear roller adjusting frame. Servo motors are respectively installed at the lower ends of the front roller adjusting frame and the rear roller adjusting frame. The output ends of the servo motors are respectively connected to the middle of a cam. The pressure acquisition mechanism is fitted against the side of the cam for the cam to contact and collect the pressure of the contact surface. The servo motor drives the cam to rotate, thereby causing the front roller or rear roller to move closer to or away from the middle roller. The pressure acquisition mechanism includes a pressure sensing mechanism and bolt B. The pressure sensing mechanism is mounted on the body by bolt B, and the acquisition end of the pressure sensing mechanism is always in contact with the side of the cam. It also includes a constant pressure decoupling control system and a material output detection system. The constant pressure decoupling control system sends commands to the servo motors of the corresponding cam drive mechanism via the CAN bus, and controls the rotation of the cams on them through the servo motors. The cams drive the left or right side of the front roller adjustment frame, or the left or right side of the rear roller adjustment frame, which serves as the transmission mechanism, to move, thereby adjusting the distance between the two sides of the front or rear roller and the middle roller. The material output detection system is used to detect whether the material output is qualified. If the detection is qualified, the material is directly discharged. If the detection is unqualified, the detection result is fed back to the constant pressure decoupling control system, which adjusts the speed of the servo motors on both sides of the front or rear roller, thereby controlling the distance between the two sides of the front or rear roller and the middle roller until the discharge is qualified. The constant pressure decoupling control system includes a touch screen system for monitoring and controlling the servo motor, a pressure ring slip mold controller, and a decoupling controller. The lower ends of both sides of the front roller adjusting frame and the rear roller adjusting frame are respectively provided with a cam drive mechanism and a pressure acquisition mechanism. The touch screen system sends commands to the servo motor of the corresponding cam drive mechanism through the CAN bus, and controls the rotation of the cam on it through the servo motor. The actual positions of the two servo motors on both sides of the front roller adjustment frame are collected using a touch screen system. The actual position of each servo motor is subtracted from the input position to obtain the tracking error. The actual position of one servo motor is multiplied by a disturbance coefficient to obtain the load disturbance of the other servo motor. This disturbance is added to the actual position of the original servo motor and then multiplied by the stress-strain pressure coefficient to obtain the actual pressure value. The difference between the actual pressure values ​​of the two servo motors is used to obtain the synchronization error. The system consists of two servo motors, servo motor A and servo motor B. For servo motor A, the input is a pressure setpoint. The pressure is converted into a position value and input to servo motor A using a calibrated stress-strain coefficient. The actual position of servo motor B is multiplied by a disturbance coefficient to obtain the load disturbance of servo motor A. The actual position of servo motor A plus the load disturbance is fed back to the input, and the difference between the input and the actual position is used to obtain the position tracking error of servo motor A. The actual position of servo motor A and the load disturbance are added together and multiplied by the stress-strain gain to obtain the actual pressure value of servo motor A. The difference between this actual pressure value and the actual pressure value of servo motor B is used as the input to the decoupling controller. The decoupling controller feeds back the pressure difference between the two sides to the pressure ring slip mode controller through the decoupling coefficient to adjust the position of the two servo motors. This allows the pressure on both sides of the front roller to stabilize after a short period of fluctuation. The rear roller uses the same control.

2. The control method for the transmission structure used for pressure control of a three-roll mill according to claim 1, characterized in that: The pressure sensing mechanism includes a metal block, a contact arc surface, a stress strain gauge, and a stress strain acquisition circuit. The upper end of the metal block is provided with a contact arc surface that always fits against the side of the cam. On the metal block, below the contact arc surface, on both sides near and away from the cam, there is a groove symmetrically provided. The groove is provided with a stress strain gauge for sensing deformation. The stress strain acquisition circuit is connected to the stress strain gauge for acquiring and transmitting signals.

3. The control method for the transmission structure used for pressure control of a three-roll mill according to claim 2, characterized in that: The pressure acquisition mechanism also includes bolt A, and the pressure sensing mechanism is mounted on the body via bolt B and bolt A which is misaligned with bolt B.

4. The control method for the transmission structure used for pressure control of a three-roll mill according to claim 1, characterized in that: The front roller adjusting frame is provided with a cam drive mechanism at the lower end of both sides of the front roller, and the rear roller adjusting frame is provided with a cam drive mechanism at the lower end of both sides of the rear roller. Each cam drive mechanism is respectively provided with a pressure acquisition mechanism.

5. The control method for a transmission structure used for pressure control of a three-roll mill according to claim 1, characterized in that: The cam is a rotationally linearized cam designed based on an involute curve.

6. The control method for the transmission structure used for pressure control of a three-roll mill according to claim 1, characterized in that: It also includes a rotating mechanism, which is connected to and drives the front roller and the rear roller to rotate respectively.

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